WHAT WATER DOES IN SOILS 53 



feet apart and let the water run through them until 

 the land is soaked. 



If we make these furrows deep enough 

 ten or twelve inches and not too 

 narrow, we can soak the land without 

 any water coming to the surface at all, 

 and so we may save quite half of the 

 water we should use in sprinkling or 

 flooding. But if we make the furrows 

 shallow, three or four inches only, 

 the water does not soak down well, and 

 we wet a good part of the surface after 

 all. Then we must wait until it dries, 

 and so lose much of the water before we 

 can close the furrows and loosen the sur- 

 face. With furrows deep enough to pre- 

 vent the water from rising to the surface 

 by wick action, we can close them imme- 

 diately after stopping the water, and leave 

 the surface dry. , 2 9ln. *2in. 



FIG. 27. Diagram 



Penetration of water. But we must showing how far 



... the water soaks 



make sure that the irrigation water down into silt and 

 in the furrow really does soak down. ^he "black 



The penetration of the water depends stands for the 



wetted soil, the 



greatly on the kind of soil (figure 27). dotted part for the 

 Sometimes, when the subsoil is hard, 

 the water may be running in the furrow for days with- 

 out penetrating a foot, and then we might as well not 

 have irrigated. The diagram (figure 28) shows (at the 



